The present invention relates to the production of electrically conductive polypyrrole and is particularly concerned with a process for converting pyrroles to conductive polypyrrole powder using chemical procedures.
Polypyrrole represents one of the most environmentally stable conducting organic polymers. Its usual preparation has involved electrochemical oxidation of pryrroles in various solvents, with films of the conducting materials depositing on the anode. Thus, free-standing polypyrrole films from about 10 .mu.m to 20 mil thick have been produced on electrodes by electrochemical polymerization. However, these prior art films are too thin and too brittle to be useful in most structurally related applications.
U.S. Pat. No. 4,552,927 to L. F. Warren discloses a conductive polypyrrole which can be produced in thicker layers and has increased mechanical flexibility as compared to prior art polypyrrole film, obtained by electropolymerizing pyrrole from an electrolyte containing a non-nucleophilic polymeric anion, such as polystyrenesulfonate, and pyrrole.
U.S. Pat. No. 4,582,575, to L. F. Warren, D. S. Klivans and L. Maus, discloses an electrically conductive composite comprising a dielectric porous substance, such as fiberglass fabric, and an electrically conductive pyrrole polymer deposited in the pores of such substance, by contacting such porous substance with an anode in an electrolytic cell containing an electrolyte comprising a pyrrole monomer and a substantially non-nucleophilic anion, such as sulfate, and electrochemically depositing a conductive pyrrole polymer in the pores of such substance. However, the resulting conductive polypyrrole does not have the bulk and ductility required to make the material useful in structural-related applications.
U.S. application Ser. No. 646,717, filed Sept. 4, 1984, of P. R. Newman, L. F. Warren, Jr., and E. F. Witucki, and assigned to the same assignee as the present application, discloses a chemical process for producing an electrically conductive composite which comprises contacting a dielectric porous substance, such as fiberglass fabric with a liquid pyrrole, contacting the porous substance with a solution of a strong oxidant capable of oxidizing pyrrole to a pyrrole polymer, such as ferric cation, and oxidizing the pyrrole in the presence of a substantially non-nucleophilic anion, such as sulfate, and precipitating a conductive pyrrole polymer in the pores of such substance.
An object of the present invention is the provision of a process for producing electrically conductive polypyrrole, which avoids electrochemical preparation.
Another object is to provide procedure for producing electrically conductive polypyrrole powder, which can be used in the production of conductive structural materials.
A still further object is the provision of electrically conductive powder produced by the above process.